The primary objective of the proposed research is to study the postnatal development of the human lateral geniculate nucleus. Using brain material obtained during normal autopsy procedures, cell cross-sectional area measurements will be made for 100 cells in each of the six laminae in the binocular segment of the lateral geniculate nucleus. In addition, similar measurements will be made in the monocular segment of the nucleus. By measuring a large number of geniculate cells in many brains it should be possible to determine the normal sequence of development in the human lateral geniculate nucleus. Once the normal sequence of development has been defined for human geniculate cells, this sequence can then be compared to the normal developmental sequences for geniculate cells in a variety of subhuman animals. If similarities exist between the developmental sequences across several species; i.e., at least in terms of geniculate cell growth, then it may be possible to relate the point in development at which visual deprivation affects normal development in an animal like the cat to a similar point in the normal development of the human visual system. The information gained from this study should help to define the 'critical-period' in the development of the human visual system. In addition, this material will be used to study the laminar patterns present in the human lateral geniculate nucleus. Our work to date indicates that at least two different patterns of lamination exist. The more usual pattern is characterized by two magnocellular laminae and four parvocellular laminae. However, in about 30% of the brains studied so far an additional two parvocellular laminae can be seen in parts of the nucleus. A secondary objective of the proposed research is to study the morphology of human geniculate and superior colliculus cells in Golgi impregnated material. These studies will be carried out primarily in tissue from adults.